now certainly the san jose area still has apple, the world's most valuable company, as well as google. >> talk about that facebook phone. >> peninsula has facebook. but the new hot start-ups, twitter, yelp, sales force, were all drawn to san francisco. several because of the city's community benefit agreement or cba. a contract whereby the city agrees to drop some taxes in exchange for economic benefits. in the case of start-up zen, the company agreed to locate in the downtrodden tenderloin. and support local jobs. in this case, a accident desk luncheon catered by a charity which trains and employs formerly homeless workers. that arrangement has become known as the twitter tax break. however, it really ought to be known as the zen tax break. mark nu. martin giles of the economist. we will talk about how -- what you have to do to san francisco to earn this. but let's start with what you get out of it. why do you want this? >> i think that -- several things drove this product. one of the things i feel personally is the most for thing is that we have a focus for the entire company. we ar